Jan 4, 2024 - Health

Shigella cluster hits Multnomah County

A photo of the bacteria shigella under a microscope

Shigella seen through a microscope. Photo: Smith Collection/Gado/Getty Images

Public health officials are tracking an antibiotic-resistant Shigella cluster in the Portland metro area this winter.

  • The tri-county area reported 227 cases in 2023, 45 of which were documented in December alone.

How it works: Shigella is a bacterial infection that causes inflammatory diarrhea, cramps and dehydration and can easily be spread from one person to another.

  • It's transmitted when a small amount of fecal matter is ingested. The most common forms of transmission are via sexual contact, changing diapers, or drinking contaminated water, according to the Centers for Disease Control and Prevention.
  • Infections involving diarrhea often go unreported, Sarah Dean, a spokesperson for Multnomah County told Axios, as "only 1 in 10 cases are actually tested and diagnosed."

What's happening: In Multnomah County, the largest clusters are among those experiencing homelessness. And despite earlier reports, Dean said there is "no clear geographic pattern to cases" to suggest the cluster is isolated to Old Town or downtown Portland.

  • A cluster is defined as a particular health event with shared characteristics, while an outbreak is when the number of clusters is higher than what is expected for a specific group and time, per the CDC.
  • Shigella has impacted Portland's homeless population and other high-risk groups since 2015.
  • Multnomah County is providing houseless individuals infected with Shigella vouchers for temporary housing "for access to shelter, water and hygiene," Dean said.

Threat level: Health officials said the risk to the general public is low, although case clusters from individual strains can last from a few weeks to a few years. One recent strain cluster lasted from November 2018 to March 2022, with 119 people affected.

  • The county will continue to monitor cases daily and prioritize communication with those at highest risk of infection.
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